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GPIOPWM(4)                   Device Drivers Manual                  GPIOPWM(4)

NAME
     gpiopwm - support for pulsing GPIO pins in software

SYNOPSIS
     gpiopwm* at gpio? offset ? mask 1
     gpiopwm* at gpio?

DESCRIPTION
     The gpiopwm driver allows for pulsing GPIO pins in software using the
     callout(9) facility.  The pulse frequency and duty cycle are specified
     indirectly by setting an "on" and "off" period, in ticks.  Both values
     are accessible as sysctl(3) variables.

SYSCTL VARIABLES
     The following sysctl(3) variables are used to define the pulsing:

     hw.gpiopwmN.off  Define the "off" period in ticks.

     hw.gpiopwmN.on   Define the "on" period in ticks.

     Only when both the "on" and the "off" period are set to values higher
     than zero pulsing will start.  To stop the pulsing, set either value to
     zero.

EXAMPLES
     To pulse a pin on a machine with 100 ticks/second with a frequency of 1Hz
     and a duty cycle of 20%, the "on" period must be set to 20 and the "off"
     period must be set to 80.  The following example will pulse the error LED
     of a Soekris net4801 with a frequency of 1 Hz and a duty cycle of 20%:

     # gpioctl gpio0 20 set pp
     # gpioctl gpio0 attach gpiopwm 20 1
     # sysctl -w hw.gpiopwm0.off=80
     # sysctl -w hw.gpiopwm0.on=20

SEE ALSO
     gpio(4), intro(4), gpioctl(8), sysctl(8)

HISTORY
     The gpiopwm driver first appeared in NetBSD 6.0.

AUTHORS
     The gpiopwm driver was written by Marc Balmer <marc@msys.ch>.

NetBSD 8.0                     November 13, 2011                    NetBSD 8.0